NIOSH Response to SC&A Review of the 

Ames Site Profile Document Regarding 

Uranium Internal Exposures 

 Rev 0 

National Institute for Occupational 

Safety and Health 

July 29, 2015 

Jackson Ellis 

Oak Ridge Associated Universities Team 

Thomas P. Tomes 

National Institute for Occupational Safety and Health 

Division of Compensation Analysis and Support 
NIOSH Response to SC&A Review of the Ames Site Profile Regarding Uranium Internal Exposures

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1.0 PURPOSE 

Sanford Cohen and Associates (SC&A) presented their review of the Site Profile for Ames 

Laboratory, ORAUT-TKBS-0055 (ORAUT 2012a) to the Advisory Board on Radiation and 

Worker Health (Advisory Board) in SCA-TR-SP2013-0044 (SC&A 2013). In this report SC&A 

presented 22 two “findings,” 11 of which included comments on some aspect or technical issue 

regarding methods of reconstructing internal dose from uranium at the Ames Laboratory. This 

paper provides additional evaluation and discussion to assist the National Institute for 

Occupational Safety and Health (NIOSH) with its response to comments on intakes of uranium, 

and ultimately in a revision to the Ames Site Profile.

2.0 SUMMARY 

The current Site Profile for Ames Laboratory (ORAUT 2012a), or Technical Basis Document 

(TBD), provides intake rates of uranium for different job categories from the three buildings 

previously used to process uranium. The TBD also provides environmental uranium intakes. The 

various uranium intakes in the TBD are based on surrogate air sampling data from other facilities 

and exposure models. 

SC&A has made numerous comments on the validity and basis of the TBD intakes, which are 

summarized in the findings listed in Section 3.1 below. SC&A also suggested some surrogate 

data from another site be used for estimating intakes from blowout incidents. NIOSH has 

reviewed the comments, the TBD methods, and available references and agrees that the uranium 

intakes in the TBD need to be reevaluated. 

In this paper, NIOSH proposes to replace the uranium intakes in the TBD with intakes derived

from bioassay data from 1944 and 1945 of workers engaged in uranium production, which 

includes some of the peak uranium production months at Ames during World War II. This is the 

bioassay data discussed in the SC&A report. Intakes in subsequent years are then derived from 

the production era intake rates. None of the current methods used to model intakes in the TBD, 

and to which SC&A had comments, are being retained in the proposed changes. Thus, this paper 

does not attempt to respond to each technical issue identified by SC&A, although Section 3.2

identifies the method being proposed to resolve each finding. 

3.0 SC&A Review 

3.1 Findings on Uranium Intakes 

SC&A identified 22 findings, 11 of which pertain to internal dose from uranium exposures. The 

11 applicable findings are listed below. Some of the findings also contain comments that apply to 

issues other than uranium; e.g., some are written to be applicable to both uranium and thorium 
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intakes. This paper only addresses uranium intakes so the findings summarized below have been 

edited to include only the pertinent information on internal uranium exposure. NOTE: The 

finding numbers are not contiguous. 

 Finding 1: Derived environmental intakes of U, as given in Table 4-7 of the TBD, are 

improperly referenced and appear without technical basis. 

 Finding 2: NIOSH provides no basis for the “assumed” losses of 0.1% of U to the 

environment and fails to identify a value for re-suspension. 

 Finding 7: The nearly “instantaneous” 100-fold reduction of U environmental intakes that 

represent the transition of the uranium metal production facilities at the end of 1953 to 

research and development (R&D) facilities in 1954 is improperly modeled. Also not included 

in the model are the contribution of blowouts to environmental contamination and the 

persistence of these radionuclides in the environment post-1953.

 Finding 9: Uranium blowouts represent significant environmental events that should be 

included in Section 4.5 of the Ames TBD for the assessment of environmental exposures. 

 Finding 10: Available empirical bioassay and air-sampling data for Annex 1 workers are 

substantially higher than modeled/surrogate data assigned by NIOSH. 

 Finding 11: NIOSH further minimized the intake value of 853 pCi/d for Annex 1 production 

workers by assigning the “distribution” as a constant.

 Finding 12: Default intake rates defined in Table 5-8 of the Ames TBD are improper for 

absorption Types F or S. 

 Finding 13: The scaling of uranium intake values based on (1) facility and (2) job function is 

without technical support and conflicts with statements given in the Ames Site Profile. 

 Finding 14: Although NIOSH briefly acknowledged the occurrence of “frequent fires and 

explosions” associated with the production of uranium metal, no attempt was made to assess 

potential intakes of these episodic events. 

 Finding 15: Technical Basis for Estimating the Maximum Plausible Dose to Workers at 

Atomic Weapons Employer Facilities, ORAUT-OTIB-0004, Rev. 03 (ORAUT 2006), is 

referenced for estimating non-operational intakes. OTIB-0004 was canceled before Rev. 03 

of the Ames Site Profile (ORAUT 2012a) was issued. Moreover, the much higher intake 

values for inhalation and ingestion during non-operating years (i.e., 1954-1976) are 
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inconsistent with intake values for operating years (1942-1953) as given in Table 5-8 of the 

Ames TBD. 

 Finding 20: By means of documented anecdotes/testimonials regarding potential frequencies 

of blowouts, technical data for a specific blowout documented at Feed Materials Production 

Center (FMPC), and reasonable assumptions, SC&A derived significant U intakes and 

associated organ doses that are applicable to workers at the Ames Laboratory, but were not 

considered/included in ORAUT-TKBS-0055 (ORAUT 2012a).

3.2 Summary of the Issues and NIOSH Resolutions 

Findings 1, 2, 7, and 9 all concern the basis for the dose models used in the TBD (ORAUT 

2012a) for environmental intakes. This paper addresses those comments by proposing a new 

method to calculate intakes. The uranium intakes presented herein include a “Low” exposure 

category based on bioassay data from workers who were incidentally exposed to uranium during 

the production years, as discussed below. This method should account for environmental intakes 

from all sources, including blowouts. Additionally, methods are presented to estimate intakes 

from a gradually depleted source term after the end of uranium production. 

In Findings 10, 11, and 12, SC&A summarizes the results of their evaluation that the TBD 

intakes for the uranium processing facilities do not account for the high bioassay results from 

workers during the uranium production years. NIOSH is now proposing to use the bioassay data 

to estimate intakes, although the methods presented by NIOSH result in intake rates somewhat 

higher than the estimates presented in the SC&A report. 

Finding 13 says the TBD does not justify the scaling of intakes based on facility and job 

function. NIOSH now proposes a simpler more favorable method to assign intakes and is 

proposing to limit the scaling of uranium intakes to three levels: High, Medium, and Low 

exposure categories, which is synonymous with intakes for operators, other exposed workers, 

and incidentally exposed workers, respectively. 

In Finding 14 and 20, SC&A identifies the lack of evaluation of intakes from blowouts, fires, and 

explosions during uranium production. They propose NIOSH use data from Fernald to estimate 

intakes at Ames from those events. The NIOSH method to evaluate Ames bioassay should 

account for intakes from these events and be more representative of intakes than data from 

another site. 

Finding 15 notes that the TBD references a canceled document and says that some workers’ 

intakes are inexplicably higher after the end of uranium production. The NIOSH evaluation of 

bioassay data and proposed new methods does not use the obsolete reference and resolves the 

discrepant intakes noted by SC&A. 
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This paper recommends a new approach be used for all uranium intakes. NIOSH determined that 

the use of uranium bioassay data collected during 1944 and 1945 is a superior approach than the 

methods used in the Ames TBD. Many of the findings above discuss discrepancies, omissions, 

and the lack of justification for methodologies that NIOSH will not be using in the next version 

of the TBD. Thus NIOSH has made no attempt to explain the rationale or to revise the existing 

TBD models in response to SC&A comments. 

A summary of Ames work with uranium is provided in Section 4. Section 5 has intake estimates 

based on bioassay data for workers during the uranium production and post-production periods. 

4.0 Ames Laboratory Uranium Work 

This section provides a summary of the uranium work at Iowa State College (ISC) and Ames 

Laboratory. Ames Laboratory was established at ISC after the end of World War II. Uranium 

work at Ames began in February 1942 when the U.S. Office of Scientific Research and 

Development (OSRD) entered into a research contract with ISC for development of methods of 

producing large quantities of high purity uranium metal in a short period of time. The Ames 

Project was under the direction of Dr. F. H. Spedding. 

The uranium work initially involved very small quantities of uranium for research, but evolved 

into uranium metal production during World War II. ISC produced a significant amount of virgin 

uranium metal and recovered metal from scrap from 1942 through the end of the war in 1945. In 

total over 1,000 tons of virgin uranium metal and recovered uranium scrap metal was produced. 

4.1 Virgin Uranium Metal Production 

The Physical Chemistry Laboratory (Chemistry Building) on the ISC campus was used for 

research and early production of uranium metal. By June 1942 ISC had developed and proven a 

method suitable for producing uranium metal from green salt (UF4), and by August 1942 they 

had developed a process that could be expanded into a production operation. The actual process 

continued to change during production as better methods were developed (ISC undateda). 

The experiments on uranium metal production from green salt resulted in the production of an 11 

pound cylinder of uranium metal on September 21, 1942. Within a week ISC was under contract 

to produce 100 pounds of uranium metal per day. With this new contract, the Ames Project 

evolved into both research and uranium metal production (Payne 1992, pdf pp. 91-96). 

A floor plan of the Chemistry Building and the rooms where the early uranium work was done 

was provided by Payne (Payne 1992, pdf p. 253). It shows room 101 where most of the early 

metal production was done. A small reduction furnace in the Chemistry Building was utilized for 
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metal production in 1942. Two tons of uranium metal were produced in the Chemistry Building 

and shipped to Chicago for use in the first self-sustaining nuclear reaction at Stagg Field on 

December 2, 1942 (Payne 1992, pdf pp. 91-96). 

In October 1942, ISC signed a contract to set up a pilot plant to produce uranium metal. The pilot 

plant was called Physical Chemistry Annex (Annex 1). Annex 1 was an existing one story 

wooden frame building that was modified and expanded to function as a temporary production 

facility until industry completed construction of uranium metal production facilities. In 

November 1942, a production contract was issued for Annex 1. Uranium reduction (UF4 to 

metal) in Annex 1 began in December 1942, although recasting of uranium metal continued to be 

done in the Chemistry Building until installation of equipment for that operation was completed 

in Annex 1 in late January 1943 (ISC undateda).

Production of virgin uranium metal went from 100 pounds per day in December 1942, to 5,600 

pounds per week by the third week of January 1943. On July 1, 1943, the peak rate of production 

was reached at 130,000 pounds per month, at which time the production rate was gradually 

reduced. Regular virgin metal production ended in November 1944 (ISC undateda; ISC 

undatedb). 

Although regular production ended in late 1944, relatively significant amounts of green salt, 

2,000 pounds per week, continued to be shipped to Ames in 1945 for use in development work 

(Simons and Hitchcock 1945). Annex 1 operated 24 hours per day, 7 days per week, during peak 

production periods (Payne 1992, pdf p. 108). 

In total more than 1.4 million pounds (700 tons) of virgin uranium metal was produced at Ames 

during the war (ISC undateda, p. 11). 

4.2 Uranium Scrap Recovery 

Large quantities of uranium scrap were generated from uranium metal machining at the various 

uranium metal processing sites during 1943 through 1945. Ames developed a method to recover 

uranium from that scrap material (ISC undateda, p. 12). 

A new plant, Annex 2, was built for scrap recovery, and scrap recovery production operations in 

Annex 2 began April 26, 1944 (Annex 2 was also used to store green salt). The uranium turnings 

were washed and dried, inspected by hand to separate foreign objects, and pressed in briquettes 

one inch thick by four and one-fourth inches in diameter. One reference indicates the 

briquettes were then sent to the casting room in Annex 1 to be melted and cast into ingots (ISC 

undatedb, p. 91). 
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The scrap recovery operations initially processed 3,000 pounds of uranium per day. Plans were 

in place to increase production to 5,000 to 6,000 pounds per day by August 1, 1944 (ISC 

undatedb, p. 49). It was reported ISC was recovering 4,000 pounds per day in October 1944, and 

that the backlog of stored turnings would be gone such that production would be reduced to 

about 2,000 pounds per day by December 1944 (ISC undatedb, p. 67). In total over 600,000 

pounds (300 tons) of uranium metal was recovered at ISC between April 1944 and the end of 

scrap recovery operations in late 1945 (ISC undateda, pp. 12-13). 

4.3 Peak Production Months 

The peak production rate for virgin uranium metal production was reported to be on July 1, 1943, 

at a rate of 130,000 per month (4,300 pounds per day), after which the production rate gradually 

declined as the raw material was gradually diverted to industry. The peak production month for 

scrap recovery is not available, but the highest production rate for scrap recovery work reported 

in available records was 4,000 pounds per day in October 1944. Records indicate regular 

production of virgin metal ended in November 1944, so some relatively small quantities of virgin 

metal would have also been produced in October 1944, but the amounts are not known. Records 

indicate all scrap recovery and virgin metal production ended in August 1945, although it is also 

reported that the scrap recovery operation was phased out in November 1945. As indicated 

above, during peak production periods ISC operated the pilot plant 24 hours per day, 7 days per 

week. 

5.0 Uranium Intakes Based on Bioassay Data 

As noted previously SC&A identified some issues with the way uranium intakes were derived in 

the TBD (ORAUT 2012a), and NIOSH agrees that some changes are needed. The uranium 

bioassay data from 1944 and 1945 that was discussed in the SC&A report was also discussed in 

the Evaluation Report for SEC 0038 (NIOSH 2006), and both reports considered the bioassay 

data to be useful for estimating intakes. NIOSH has reviewed that data and determined that it 

provides a better means to estimate occupational intakes during the uranium production period at 

ISC than the methods presented in the TBD. NIOSH plans to eliminate the multiple facilityspecific uranium intake rates that are currently in the TBD because neither the bioassay data nor 

information on worker location is sufficient for that determination. 

5.1 Analysis of Bioassay Data 

The Ames bioassay data are reported by Ferretti, et al. (1951, pdf pp. 267-279). The bioassay 

data were collected for a study on the urinary excretion of uranium at some Manhattan Project 

sites. The data from Tables 7.1 through 7.4 in that reference are data from the Ames project and 

were used to estimate intakes from uranium production operations at Ames. These data are 
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believed to be the best available data for estimating intakes for uranium operations at Ames. 

Table 1 below presents the Ames bioassay data from Ferretti et al. (1951). 

Table 1: Bioassay Data

Group Sample Case Concentration (μg/L)

1 1 1 40

1 2 1 96

1 3 2 52

1 4 3 86

1 5 3 50

1 6 4 100

1 7 4 44

1 8 4 70

1 9 4 200

1 10 5 126

1 11 5 96

1 12 5 74

1 13 6 84

1 14 6 200

1 15 6 73

1 16 7 48

1 17 7 40

1 18 8 29

1 19 9 25

1 20 10 12

1 21 11 31

2 1 12 15

2 2 13 17

2 3 14 13

2 4 15 38

2 5 16 21

2 6 17 40

2 7 18 21

2 8 19 33

2 9 19 58

2 10 20 33

2 11 21 54

2 12 22 64

2 13 23 10

2 14 23 16
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Table 1: Bioassay Data

Group Sample Case Concentration (μg/L)

2 15 24 11

2 16 24 11

2 17 25 87

2 18 25 64

2 19 25 80

2 20 26 130

2 21 27 80

2 22 28 108

2 23 29 64

2 24 29 64

2 25 30 28

2 26 31 43

3 1 32 24

3 2 33 27

3 3 34 7

3 4 35 9

3 5 36 19

3 6 37 22

3 7 38 22

3 8 38 18

3 9 38 3

3 10 38 3

3 11 39 5

3 12 40 18

3 13 41 15

3 14 42 33

4 1 43 <3 

4 2 44 <3 

4 3 45 7

4 4 46 <3 

4 5 47 <3 

4 6 48 9

Source: Ferretti et al., 1951 

The data reported 67 sample results from 48 workers, who were ranked by their supervisor into 

four exposure categories according to potential for exposure to uranium. Group 1 was expected 

to be the highest (greatest amount of uranium exposure); Group 2 (next highest amount of 

uranium exposure); Group 3 (very little, but continuous exposure); and Group 4, the lowest 

exposure (occasional incidental exposure). The workers were given strict instructions to avoid 
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sample contamination. Samples were submitted between September 1944 and July 1945 (Ferretti 

et al. 1951). 

Bioassay sample dates were not provided; however, the data reflect that some individuals were 

assessed more than once, at intervals of a few weeks or months. For this analysis, all unique 

combinations of individual (Case) and group (Group) are considered to be unique individuals. If 

an individual has more than one result, a mean was calculated, thereby having one result for each 

individual. A One-Person, One-Statistic (OPOS) approach, as described in ORAUT-RPRT-0053, 

Analysis of Stratified Coworker Datasets (ORAUT 2014a), was performed. A regression on 

order statistics (ROS) fit to the OPOS data was performed, providing the following data: 

Geometric Mean (GM) = 24.69 μg/L; Geometric Standard Deviation (GSD) = 2.788 

From these parameters: 

The 50th percentile bioassay result is estimated by: 

giving: 

The 84th percentile bioassay result is estimated by: 

giving: 

These data were evaluated with Integrated Modules for Bioassay Analysis (IMBA) to obtain 

uranium intake rates for calculation of internal doses to workers. The following parameters were 

used.

 Start of chronic intake is 9/1/1942 (production of uranium metal began in earnest in 

September 1942 at Ames). 
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 Date of the urine sample is 1/31/1945, which is midway between 9/1/1944 and 7/1/1945 

(date range given in Ferretti et al. [1951] for bioassay samples). 

 The chronic intake continues through the effective sample date of 1/31/1945.

 The specific activity of natural uranium (0.68296 pCi/μg) was used to convert the mass 

intake rates to activity intake rates. 

 Based on process information, it is presumed that workers could have been exposed to 

solubility Types F, M, or S materials. 

The 50th percentile intake rates are: 

 Type F: 86.46 pCi/day 

 Type M: 354.5 pCi /day 

 Type S: 6932 pCi /day 

The 84th percentile intake rates are: 

 Type F: 241.1 pCi/day 

 Type M: 988.4 pCi /day 

 Type S: 19,326 pCi /day 

5.2 Worker Exposure Categories 

In accordance with ORAUT-OTIB-0060, Internal Dose Reconstruction (ORAUT 2014b):

Coworker dose is applied as a best estimate for individuals with a potential for intakes of 

radioactive material but who lack bioassay data or have unmonitored intervals. Workers 

with a significant potential for intake should be assigned doses at the 95th percentile with a 

constant distribution, while those with less potential are assigned the 50th percentile with a 

lognormal distribution. 

ORAUT-OTIB-0014, Assignment of Environmental Internal Doses for Employees Not Exposed 

to Airborne Radionuclides in the Workplace (ORAUT 2004), provides guidance on job 

categories and potential for exposure. 

Dose reconstructors will use the information from these references and the category information 

below to assign intakes to Ames workers. 
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High (Assign 95th percentile intakes) – Individuals who operated the process equipment and/or 

routinely handled radiological materials. This category would include operators, maintenance 

workers, laboratory workers, health physics monitors, etc. Doses will be applied as a constant. 

Medium (Assign 50th percentile intakes) – Individuals who routinely worked in the production 

areas and may have been periodically in the vicinity of where processing was occurring. This 

includes supervisory staff, engineers, individuals who were not normally in contact with the 

radiological materials but who worked routinely in the production areas, etc. Doses will be 

applied as a lognormal distribution. 

Low – This category is for individuals exposed to ambient air in the environment outside of the 

uranium production areas who may have been incidentally exposed. This includes office workers 

or non-uranium workers who are documented to have been in a different location from the 

uranium work. These intakes allow for incidental exposures and will be applied as a constant. 

The rationale for this value is provided below. 

As discussed above, uranium bioassay data is available for 48 workers who were involved in 

uranium production in 1944 and 1945. The supervisor listed six of those workers as Group 4 

workers perceived to only have only incidental occasional exposure to uranium. The distribution 

of the bioassay results for the four groups are consistent with those rankings, with some 

overlapping of the range of results. Of the six workers in the Group 4 category, four workers had 

a bioassay result of <3 μg/L, one worker had a result of 7 μg/L, and one worker had a result of 9 

μg/L. 

The Group 4 workers presumably would have been exposed to both ambient air outside of the 

production facilities and occasional incidental exposure to uranium work areas; therefore, the 

highest result from that group of workers should provide a bounding estimate for workers in 

other (non-uranium) facilities or locations. An intake rate derived from this value will be used for 

the Low category of intakes and be applied as a constant. 

5.3 Intake Calculations 

Intakes are provided for the High, Medium, and Low exposure categories. 

High

The High intake category is the 95th percentile of the intake distribution and is applied as a 

constant value in the Interactive RadioEpidemiological Program (IREP). Per ORAUT-OTIB0060, the GSD was rounded up to 3.0. The calculation of the 95th percentile intakes are derived 

from the 50th percentile (GM) intakes given above with the GSD rounded up to 3.0, according to 

the equation: 
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where GSD = 3.0 

The 95th percentile intake rates are then: 

 Type F: 526.9 pCi/day 

 Type M: 2160 pCi /day 

 Type S: 42,240 pCi /day 

Medium 

The medium intake category are the 50th percentile intake values above in Section 5.1 and are 

applied as a lognormal distribution with the GSD rounded up to 3. 

 Type F: 86.46 pCi/day 

 Type M: 354.5 pCi /day 

 Type S: 6932 pCi /day 

Low 

The low intake category is based on an excretion rate of 9 μg/L with the parameters discussed in 

Section 5.1. Those values were input into IMBA to determine the following intake rates:

 Type F: 31.52 pCi/day 

 Type M: 129.2 pCi /day 

 Type S: 2525 pCi /day 

5.4 Assignment of Internal Exposures 

The intakes were derived from bioassay taken during the uranium production. Uranium 

production activities in both Annex 1 and Annex 2 ended in 1945. Production work in the 

Chemistry Building had ended in 1943. There were continuing activities in all three buildings 

after 1945. 

Records of decontamination activities for the Chemistry Building are currently unavailable, 

although records for later years indicated the building had been remodeled. 

After 1945 Annex 1 continued to operate producing thorium for a few years. No 

decontamination information is available. The facility was demolished in 1953, although there 

are currently no available radiological monitoring data from the demolition work. 
NIOSH Response to SC&A Review of the Ames Site Profile Regarding Uranium Internal Exposures 

Page 14 of 20

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in 

discussions with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final 

NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents 

preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and 

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The use of Annex 2 after 1945 is not clear and it is not known if or when the facility was 

decontaminated. However, Annex 2 was sold by the Atomic Energy Commission to ISC in 1953 

and used as a Plumbing Shop until it was razed in 1972. 

To allow for potential intakes of uranium after the end of 1945, the production era intake rates 

are to be applied through 1953 for the Chemistry Building, Annex 1 and Annex 2. Additionally, 

that intake rate is also applied for the 1972 demolition of Annex 2. 

Workers at the uranium production facilities could have been exposed to uranium with solubility 

types of F, M, and S. Dose reconstructors will select the material type that provides the highest 

dose. These calculated intake rates presume that the period of the bioassay results included 

normal uranium production operations, including blowout and fire events. 

Tables 2, 3, and 4 show the inhalation intakes for the three categories of exposure. All intakes are 

calendar day intake rates. 

Table 2: 95th Percentile Intakes (For Employees with High Exposure Potential)

Nuclide Solubility Intake 

Type

Intake Rate (pCi/day)

1942-1953, 1972 Distribution

U-234 F Inhalation 526.9 Constant

U-234 M Inhalation 2160 Constant

U-234 S Inhalation 42,240 Constant

Table 3: 50th Percentile Intakes (For Employees with Medium Exposure Potential)

Nuclide Solubility Intake 

Type

Intake Rate (pCi/day)

1942-1953, 1972 Distribution GSD

U-234 F Inhalation 86.46 Lognormal 3.0

U-234 M Inhalation 354.5 Lognormal 3.0

U-234 S Inhalation 6,932 Lognormal 3.0
NIOSH Response to SC&A Review of the Ames Site Profile Regarding Uranium Internal Exposures 

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in 

discussions with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final 

NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents 

preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and 

redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

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Table 4: Low Intakes (For Employees with only Incidental Exposure Potential)

Nuclide Solubility Intake 

Type

Intake Rate (pCi/day)

1942-1953, 1972 Distribution

U-234 F Inhalation 31.52 Constant

U-234 M Inhalation 129.2 Constant

U-234 S Inhalation 2,525 Constant

5.5 Residual Radioactivity Period Environmental Uranium Exposure 

After 1953, the internal exposure potential to uranium was reduced and continued to be reduced 

throughout the operation of the site. The median (50th percentile) intake rates derived above were 

used to estimate surface contamination levels based on a 30-day suspension as discussed in 

Battelle-TBD-6000, Section 3.4.2 (Battelle 2011). The contamination levels were multiplied by a 

re-suspension factor of 1 x 10-5/m and a breathing rate of 9.6 m3/d to determine the following 

inhalation intake rates: 

 Type F: 1.681 pCi/day 

 Type M: 6.891 pCi /day 

 Type S: 134.8 pCi /day 

These intake rates are applicable for 1954. For subsequent years, a gradual reduction of the 

contaminants is presumed in accordance with depletion factors provided in ORAUT-OTIB-0070, 

Dose Reconstruction During Residual Radioactivity Periods at Atomic Weapons Employer 

Facilities (ORAUT 2012b). A depletion rate of 0.00067 per day was used to determine annual 

depletion factors, as presented in ORAUT-OTIB-0070, Table 4-2. 

Table 5 below presents the inhalation intake rates from residual radioactivity. The intakes will be 

assigned using a lognormal distribution and a GSD of 3.0. Annex 2 was demolished in 1972, and 

the radiological status of the facility at that time is not clear; therefore, the operational intake 

rates (from the 1942-1953 period) will be assigned for Annex 2 work that year. 
NIOSH Response to SC&A Review of the Ames Site Profile Regarding Uranium Internal Exposures 

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in 

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NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents 

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redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

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Table 5: Uranium Inhalation Intakes from Residual Contamination

Annual Reduction Factors Intakes (pCi/day)1

Lognormal Distribution; GSD = 3

Year Factor F M S

1954 1.00E+00 1.68 6.89 134.8

1955 7.83E-01 1.32 5.40 105.5

1956 6.13E-01 1.03 4.22 82.61

1957 4.80E-01 0.81 3.31 64.68

1958 3.76E-01 0.63 2.59 50.67

1959 2.94E-01 0.49 2.03 39.62

1960 2.31E-01 0.39 1.59 31.13

1961 1.81E-01 0.30 1.25 24.39

1962 1.41E-01 0.24 0.97 19.00

1963 1.11E-01 0.19 0.76 14.96

1964 8.67E-02 0.15 0.60 11.68

1965 6.79E-02 0.11 0.47 9.15

1966 5.32E-02 0.089 0.37 7.17

1967 4.16E-02 0.070 0.29 5.61

1968 3.26E-02 0.055 0.22 4.39

1969 2.55E-02 0.043 0.18 3.44

1970 2.00E-02 0.034 0.14 2.70

1971 1.56E-02 0.026 0.11 2.10

19722 1.23E-02 0.021 0.085 1.66

1973 9.60E-03 0.016 0.066 1.29

1974 7.51E-03 0.013 0.052 1.01

1975 5.88E-03 0.010 0.041 0.79

1976 4.61E-03 0.0077 0.032 0.62

1977 3.61E-03 0.0061 0.025 0.49

1978 2.83E-03 0.0048 0.020 0.38

1979 2.21E-03 0.0037 0.015 0.30

1980 1.73E-03 0.0029 0.012 0.23

1981 1.36E-03 0.0023 0.0094 0.18

1982 1.06E-03 0.0018 0.0073 0.14

1983-end 8.32E-04 0.0014 0.0057 0.11

1

Intake rates are normalized to calendar days. 

2For 1972, use Tables 2, 3, and 4 for workers potentially exposed to demolition of Annex 2. 
NIOSH Response to SC&A Review of the Ames Site Profile Regarding Uranium Internal Exposures 

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in 

discussions with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final 

NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents 

preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and 

redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

. 

Ingestion intakes during the residual period are estimated from the derived surface contamination 

levels using the methods specified in OCAS-TIB-009 (DCAS 2004). The annual ingestion rates 

were then determined by multiplying the initial intake rate by the annual reduction factors shown 

in Table 5 above. Ingestion intakes are provided in Table 6. 

Table 6: Uranium Ingestion Intakes from Residual Contamination

Annual Reduction Factors Intakes (pCi/day)1

Lognormal Distribution; GSD = 3

Year Factor F M S

1954 1.00E+00 3.5E-02 1.4E-01 2.8E+00

1955 7.83E-01 2.7E-02 1.1E-01 2.2E+00

1956 6.13E-01 2.1E-02 8.8E-02 1.7E+00

1957 4.80E-01 1.7E-02 6.9E-02 1.3E+00

1958 3.76E-01 1.3E-02 5.4E-02 1.1E+00

1959 2.94E-01 1.0E-02 4.2E-02 8.3E-01

1960 2.31E-01 8.1E-03 3.3E-02 6.5E-01

1961 1.81E-01 6.3E-03 2.6E-02 5.1E-01

1962 1.41E-01 4.9E-03 2.0E-02 4.0E-01

1963 1.11E-01 3.9E-03 1.6E-02 3.1E-01

1964 8.67E-02 3.0E-03 1.2E-02 2.4E-01

1965 6.79E-02 2.4E-03 9.7E-03 1.9E-01

1966 5.32E-02 1.9E-03 7.6E-03 1.5E-01

1967 4.16E-02 1.5E-03 6.0E-03 1.2E-01

1968 3.26E-02 1.1E-03 4.7E-03 9.2E-02

1969 2.55E-02 8.9E-04 3.7E-03 7.2E-02

1970 2.00E-02 7.0E-04 2.9E-03 5.6E-02

1971 1.56E-02 5.5E-04 2.2E-03 4.4E-02

19722 1.23E-02 4.3E-04 1.8E-03 3.5E-02

1973 9.60E-03 3.4E-04 1.4E-03 2.7E-02

1974 7.51E-03 2.6E-04 1.1E-03 2.1E-02

1975 5.88E-03 2.1E-04 8.4E-04 1.7E-02

1976 4.61E-03 1.6E-04 6.6E-04 1.3E-02

1977 3.61E-03 1.3E-04 5.2E-04 1.0E-02

1978 2.83E-03 9.9E-05 4.1E-04 7.9E-03

1979 2.21E-03 7.7E-05 3.2E-04 6.2E-03
NIOSH Response to SC&A Review of the Ames Site Profile Regarding Uranium Internal Exposures 

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in 

discussions with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final 

NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents 

preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and 

redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

. 

Table 6: Uranium Ingestion Intakes from Residual Contamination

Annual Reduction Factors Lo

Intakes (pCi/day)1

gnormal Distribution; GSD = 3

Year Factor F M S

1980 1.73E-03 6.1E-05 2.5E-04 4.9E-03

1981 1.36E-03 4.8E-05 2.0E-04 3.8E-03

1982 1.06E-03 3.7E-05 1.5E-04 3.0E-03

1983-end 8.32E-04 2.9E-05 1.2E-04 2.3E-03 1

Intake rates are normalized to calendar days. 

6.0 References 

Battelle (Battelle Memorial Institute), (2011) Battelle-TBD-6000, Technical Basis Document: 

Site Profiles for Atomic Weapons Employers That Worked Uranium Metals, Rev 1, June 

17, SRDB Reference ID 101251.

Day, H.S., (1980) The Iowa State University Campus and its Buildings, SRDB Reference ID 

143348.

DCAS, (2004) Estimation of Ingestion Intakes, OCAS-TIB-009, Office of Compensation 

Analysis and Support, Cincinnati, Ohio, April 13.

Ferretti, R.J.; G.R. Price; and S. Schwartz, (1951) Uranium Excretion Studies, in: Industrial 

Medicine on the Plutonium Project: Survey and Collected Papers, edited by Robert S. 

Stone. New York: McGraw-Hill Book Co. SRDB Reference ID 739. 

ISC (Iowa State College), (undateda), Final Report, Iowa State College Contract No. 7405 - eng 

7, author unknown, SRDB Reference ID 93764. 

ISC (Iowa State College), (undatedb), History of the Iowa State College Contract W 7405-eng 7,

author unknown, pdf pp. 48-75, SRDB Reference ID 8864. 

NIOSH, (2006) SEC Petition Evaluation Report, Petition SEC-00038 (Ames Laboratory), 

National Institute for Occupational Safety and Health, Office of Compensation Analysis 

and Support, Cincinnati, Ohio, April 9, SRDB Reference ID 51256. 

NIOSH, (2007) SEC Petition Evaluation Report, Petition SEC-00075 (Ames Laboratory), 

National Institute for Occupational Safety and Health, Office of Compensation Analysis 

and Support, Cincinnati, Ohio, May 09, SRDB Reference ID 54551. 
NIOSH Response to SC&A Review of the Ames Site Profile Regarding Uranium Internal Exposures 

Page 19 of 20

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in 

discussions with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final 

NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents 

preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and 

redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

. 

NIOSH, (2010) SEC Petition Evaluation Report, Petition SEC-00166 (Ames Laboratory), 

National Institute for Occupational Safety and Health, Office of Compensation Analysis 

and Support, Cincinnati, Ohio, July 26, SRDB Reference ID 94025. 

NIOSH, (2011) SEC Petition Evaluation Report, Petition SEC-00185 (Ames Laboratory), 

National Institute for Occupational Safety and Health, Office of Compensation Analysis 

and Support, Cincinnati, Ohio, June 7, SRDB Reference ID 99020. 

ORAUT (Oak Ridge Associated Universities Team), (2004) Technical Information Bulletin:

Assignment of Environmental Internal Doses for Employees Not Exposed to Airborne 

Radionuclides in the Workplace, ORAUT-OTIB-0014, Rev 00, Oak Ridge, Tennessee, 

June 22, SRDB Reference ID 19432. 

ORAUT (Oak Ridge Associated Universities Team), (2012a) ORAUT-TKBS-0055, Site Profile 

for Ames Laboratory, Rev 03, January 3, 2012, SRDB Reference ID 106103. 

ORAUT (Oak Ridge Associated Universities Team), (2012b) ORAUT-OTIB-0070, Technical 

Information Bulletin: Dose Reconstruction during Residual Radioactivity Periods at 

Atomic Weapons Employer Facilities, Rev 01, March 5, SRDB Reference ID 108851. 

ORAUT (Oak Ridge Associated Universities Team), (2014a) ORAUT-RPRT-0053, Analysis of 

Stratified Coworker Datasets, Rev 02, October 08, SRDB Reference ID 136245. 

ORAUT (Oak Ridge Associated Universities Team), (2014b) ORAUT-OTIB-0060, Technical 

Information Bulletin: Internal Dose Reconstruction, Rev 01, September 8, SRDB 

Reference ID 135808. 

Payne, C.S., (1992) The Ames Project: Administering Classified Research as a Part of the 

Manhattan Project at Iowa State College, 1942-45, PhD dissertation, Iowa State 

University, Ames, Iowa, SRDB Reference ID 18851.

SC&A (Sanford Cohen & Associates), (2013) Review of the NIOSH Site Profile for the Ames 

Laboratory, SCA-TR-SP2013-0044, August 14.

SC&A (Sanford Cohen & Associates), (2007) The Relevance of the 250-Workday Requirement 

to Potential Exposures Associated with a Single Blowout.

Simons, F.W. and G. E. Hitchcock, (1945), Internal Manhattan Engineer District 

Correspondence, February 15, SRDB Reference ID 9161. 

Tybout, R. A., (1944) letter to F. H. Spedding (Iowa State College), U.S. Army Corps of 

Engineers, July 17, SRDB Reference ID 8959, pp. 8-9.
NIOSH Response to SC&A Review of the Ames Site Profile Regarding Uranium Internal Exposures 

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in 

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NIOSH or ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents 

preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and 

redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

. 

Wilhelm, H. A., (1960) Development of Uranium Metal Production in America, SRDB 

Reference ID 18824.